Patterning of multi-depth optical devices

ABSTRACT

Methods for patterning of multi-depth layers for the fabrication of optical devices are provided. In one embodiment, a method is provided that includes disposing a resist layer over a device layer disposed over a top surface of a substrate, the device layer having a first portion and a second portion, patterning the resist layer to form a first resist layer pattern having a plurality of first openings and a second resist layer pattern having a plurality of second openings, and etching exposed portions of the device layer defined by the plurality of first openings and the plurality of second openings, wherein the plurality of first openings are configured to form at least a portion of a plurality of first structures within the optical device, and the plurality of second openings are configured to form at least a portion of a plurality of second structures within the optical device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/832,807, filed on Apr. 11, 2019, which herein isincorporated by reference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to opticaldevices. More specifically, embodiments described herein provide forpatterning multi-depth layers for the fabrication of optical devices.

Description of the Related Art

Optical devices may be used to manipulate the propagation of light byspatially varying structural parameters (e.g., shape, size, orientation)of structures of the optical devices formed on a substrate. The opticaldevices provide a spatially varying optical response that molds opticalwavefronts as desired. These structures of the optical devices alterlight propagation by inducing localized phase discontinuities (i.e.,abrupt changes of phase over a distance smaller than the wavelength ofthe light). These structures may be composed of different types ofmaterials, shapes, or configurations on the substrate and may operatebased upon different physical principles.

Fabricating optical devices requires forming structures from a devicelayer disposed on the substrate. However, the desired properties of anoptical device to be fabricated may necessitate structures havingvarious depths. Forming structures with various depths from may requirepatterning multiple layers disposed adjacently over the substrate.Accordingly, what is needed in the art are methods for patterning ofmulti-depth layers for the fabrication of optical devices.

SUMMARY

Methods for patterning of multi-depth layers for the fabrication ofoptical devices are provided. In one embodiment, a method is providedthat includes disposing a resist layer over a device layer disposed overa top surface of a substrate, the device layer having a first portionhaving a first height from the top surface of the substrate and a secondportion having a second height from the top surface of the substrate,patterning the resist layer to form a first resist layer pattern havinga plurality of first openings formed therein over the first portion ofthe device layer and form a second resist layer pattern having aplurality of second openings formed therein over the second portion ofthe device layer, and etching exposed portions of the device layerdefined by the plurality of first openings and the plurality of secondopenings, wherein the plurality of first openings in the first resistlayer pattern are configured to form at least a portion of a pluralityof first structures within the optical device, and the first structureshave a first depth relative to the top surface of the substrate, and theplurality of second openings in the second resist layer pattern areconfigured to form at least a portion of a plurality of secondstructures within the optical device, and the second structures have asecond depth relative to the top surface of the substrate.

In another embodiment, a method is provided that includes disposing ahardmask over a device layer disposed over a top surface of a substrate,the device layer having a first portion having a first height from thetop surface of the substrate and a second portion having a second heightfrom the top surface of the substrate, disposing a resist layer over thehardmask, the resist layer having a top surface parallel to the topsurface of the substrate, patterning the resist layer to form a firstresist layer pattern having a plurality of first openings formed thereinover the first portion of the device layer and form a second resistlayer pattern having a plurality of second openings formed therein overthe second portion of the device layer, etching exposed portions of thehardmask defined by the plurality of first openings and the plurality ofsecond openings to expose unmasked first device layer segments of thefirst portion of the device layer and expose unmasked second devicelayer segments of the second portion of the device layer, and etchingthe first device layer segments and the second device layer segments,wherein the first device layer segments are configured to form at leasta portion of a plurality of first structures within the optical device,and the first structures have a first depth relative to the top surfaceof the substrate and the second device layer segments are configured toform at least a portion of a plurality of second structures within theoptical device, and the second structures have a second depth relativeto the top surface of the substrate.

In yet another embodiment, a method is provided that includes disposinga planarization layer over a device layer disposed over a top surface ofa substrate, the device layer having a first portion having a firstheight from the top surface of the substrate and a second portion havinga second height from the top surface of the substrate, disposing aresist layer over the planarization layer, patterning the resist layerto form a first resist layer pattern having a plurality of firstopenings formed therein over the first portion of the device layer andform a second resist layer pattern having a plurality of second openingsformed therein over the second portion of the device layer, etchingexposed portions of the planarization layer defined by the plurality offirst openings and the plurality of second openings to expose unmaskedfirst device layer segments of the first portion of the device layer andexpose unmasked second device layer segments of the second portion ofthe device layer, and etching the first device layer segments and thesecond device layer segments, wherein the first device layer segmentsare configured to form at least a portion of a plurality of firststructures within the optical device, and the first structures have afirst depth relative to the top surface of the substrate, and the seconddevice layer segments are configured to form at least a plurality ofsecond structures within the optical device, and the second structureshave a second depth relative to the top surface of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited structures of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, and may admit to other equally effective embodiments.

FIG. 1A is a schematic, perspective view of an optical device accordingto one embodiment.

FIG. 1B is a schematic, cross-sectional view of the optical device ofFIG. 1A.

FIG. 2A is a schematic, perspective view of an optical device accordingto one embodiment.

FIG. 2B is a schematic, cross-sectional view of the optical device ofFIG. 2A.

FIG. 3 is a flow diagram of a method for forming an optical deviceaccording to an embodiment.

FIGS. 4A-4E are schematic, cross-sectional views of a substrate during amethod of forming an optical device according to an embodiment.

FIG. 5 is a flow diagram of a method for forming an optical deviceaccording to an embodiment.

FIGS. 6A-6D are schematic, cross-sectional views of a substrate during amethod of forming an optical device according to an embodiment.

FIG. 7 is a flow diagram of a method for forming an optical deviceaccording to an embodiment.

FIGS. 8A-8D are schematic, cross-sectional views of a substrate during amethod of forming an optical device according to an embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and structures of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to patterning multi-depthlayers for the fabrication of optical devices.

FIG. 1A is a schematic, perspective view of an optical device 100. Inone embodiment, the optical device 100 is a waveguide combiner, forexample an augmented reality waveguide combiner. It is to be understoodthat the optical device 100 described below is an exemplary waveguidecombiner. The optical device 100 includes a substrate 101, a firstgrating 102 defined by a plurality of structures 103, and a secondgrating 105 defined by a plurality of structures 106. In one embodiment,the structures 103 and the structures 106 are nanostructures havingsub-micron critical dimensions, e.g., nano-sized critical dimensions.

FIG. 1B is a schematic, cross-sectional view of the optical device 100according to FIG. 1A. The optical device 100 includes a plurality ofstructures 103 having two or more depths. As shown in FIG. 1B, aplurality of first structures 114 have a first depth 116 to a topsurface 118 of the substrate 101, and a plurality of second structures115 have a second depth 117 to the top surface 118 of the substrate 101.The first depth 116 and the second depth 117 are different. For example,as shown in FIG. 1B, the first depth 116 is less than the second depth117. In one embodiment, the structures 103 are at an angle with regardto the top surface 118 of the substrate 101. In another embodiment, thestructures 103 are perpendicular to the top surface 118 of the substrate101.

FIG. 2A is a schematic, perspective view of an optical device 200 havingone or more structures 203 according to embodiments described herein. Insome embodiments, the optical device 200 is a flat optical device, suchas a metasurface. The one or more structures 203 are disposed on thesubstrate 101. While FIG. 2A depicts the one or more structures 203 ashaving square or rectangular cross-sections, the cross-sections of theone or more structures 203 may have other shapes including, but notlimited to, circular, triangular, and/or irregular shapedcross-sections. In one embodiment, the structures 203 are nanostructureshaving sub-micron critical dimensions, e.g., nano-sized criticaldimensions.

FIG. 2B is a schematic, cross-sectional view of the optical device 200according to FIG. 2A. The optical devices 200 includes one or morestructures 203, such as one or more first structures 214 and one or moresecond structures 215 disposed on the substrate 101. The one or morefirst structures 214 have a first depth 216 to the top surface 118 ofthe substrate 101. The one or more second structures 215 have a seconddepth 217 to the top surface 188 of the substrate 101. The first depth216 and the second depth 217 are different. For example, as shown inFIG. 2B, the first depth 216 is less than the second depth 217. In oneembodiment, the structures 203 are at an angle with regard to the topsurface 118 of the substrate 101. In another embodiment, the structures203 are perpendicular to the top surface 118 of the substrate 101.

The substrate 101 may be selected to transmit a suitable amount of lightof a desired wavelength or wavelength range, such as one or morewavelengths in the infrared region to UV region (i.e., from about 700 toabout 1500 nanometers). Without limitation, in some embodiments, thesubstrate 101 is configured such that the substrate 101 transmitsgreater than or equal to about 50%, 60%, 70%, 80%, 90%, 95%, 99%, to UVregion of the light spectrum. The substrate 101 may be formed from anysuitable material, provided that the substrate 101 can adequatelytransmit light in a desired wavelength or wavelength range and can serveas an adequate support for the optical devices. In some embodiments, thematerial of substrate 101 has a refractive index that is relatively low,as compared to the refractive index of the device material. Substrateselection may include substrates of any suitable material, including,but not limited to, amorphous dielectrics, crystalline dielectrics,silicon oxide, polymers, and combinations thereof. In some embodiments,the substrate 101 includes a transparent material. In one embodiment,the substrate 101 is transparent with absorption coefficient smallerthan 0.001. Suitable examples may include an oxide, sulfide, phosphide,telluride, or combinations thereof.

In some embodiments, the optical devices 100, 200 described hereininclude first structures 114, 214 having first depths 116, 216 andsecond structures 115, 215 having second depths 117, 217 disposed in thesubstrate 101. In the embodiments described herein of the methods 300,500, and 700 for the forming optical devices 100, 200, the substrate 101has a first height 404 and a second height 405 (shown in FIG. 4A). Thefirst height 404 corresponds to the first depth 116, 216 of the firststructures 114, 214 to be formed, and the second height 405corresponding to the second depth 117, 217 of the plurality of secondstructures 115, 215 to be formed in the substrate 101.

In other embodiments, the optical devices 100, 200 described hereininclude first structures 114, 214 having first depths 116, 216 andsecond structures 115, 215 having second depths 117, 217 are disposedover the substrate 101. The first structures 114, 214 and the secondstructures 115, 215 are formed from a device layer 408. Prior to themethods 300, 500, and 700, the device layer 408 has a first height 411and a second height 412. The first height 411 corresponds to the firstdepth 116, 216 of the first structures 114, 214 to be formed, and thesecond height 412 corresponds to the second depth 117, 217 of theplurality of second structures 115, 215 to be formed.

FIG. 3 is a flow diagram of a method 300 for forming a portion of anoptical device 100, 200 according to embodiments described herein. FIGS.4A-4E are schematic, cross-sectional views of the substrate 101 during amethod of forming a portion of an optical device 100 or an opticaldevice 200 according to an embodiment. The portion may correspond to onegrating, such as the first grating 102 or second grating 105, or theportion may correspond to the entirety of the optical device 100 oroptical device 200.

FIG. 4A illustrates an embodiment, in which a resist layer 407 isdisposed on the substrate 101. In one embodiment, the substrate 101 ispatterned, the substrate 101 having first height 404 and second height405 for achieving first structures 114, 214 and second structures 115,215 of various heights. FIG. 4B illustrates an embodiment in which theresist layer 407 is disposed on a device layer 408 and the device layer408 is disposed on the top surface 118 of the substrate 101. In oneembodiment, the device layer 408 is patterned, the device layer havingfirst height 411 and second height 412 for achieving first structures114, 214 and second structures 115, 215 of various heights.

In one embodiment, the resist layer 407 includes a silicon-containingmaterial. In another embodiment, the resist layer 407 includes anorganic material. The resist layer 407 is deposited on the substrate 101through any suitable method, such as a liquid material pour castingprocess, a spin-on coating process, a liquid spray coating process, adry powder coating process, a screen printing process, a doctor bladingprocess, a physical vapor deposition (PVD) process, a chemical vapordeposition (CVD) process, a flowable CVD (FCVD) process, or an atomiclayer deposition (ALD) process. The thickness of the resist layer 407 isselected in order to tune the etch process and the resulting criticaldimensions of the plurality of structures 103. For example, a greaterthickness of the resist layer 407 can result in smaller criticaldimensions of the plurality of structures 103. In one embodiment, thethickness of the resist layer 407 ranges from about 50 nm to about 300nm. In one embodiment, the resist layer 407 has a first thickness 409and a second thickness 410. The first thickness 409 may be greater orless than the second thickness 410. The first thickness 409 will resultin the first structures 114, 214 having the first depths 116, 216. Thesecond thickness 410 will result in the second structures 115, 215having the second depths 117, 217.

According to one embodiment, the device layer 408 includes, but is notlimited to, one or more of titanium dioxide (TiO₂), zinc oxide (ZnO),tin dioxide (SnO₂), aluminum-doped zinc oxide (AZO), fluorine-doped tinoxide (FTO), cadmium stannate (tin oxide) (CTO), niobium oxide (Nb₂O₅),and zinc stannate (tin oxide) (SnZnO₃), silicon nitride (Si₃N₄), andamorphous silicon (a-Si) containing materials. In one embodiment, theheight of the device layer 408 ranges from about 20 nm to about 200 nm.As shown in FIG. 3, the resist layer 407 is disposed on the device layer408 at step 301. The device layer 408 includes a first portion 424having first height 411 from the surface of the substrate and a secondportion 425 having second height 412 from the surface of the substrate.The first height 411 corresponds to the first structures 114, 214 to beformed, and the second height 412 corresponds to the second structures115, 215 to be formed.

The embodiment of FIG. 4A illustrates a 1:1 etch rate in which theresist layer 407 is etched at approximately the same rate as the devicelayer 408. The embodiment of FIG. 4D illustrates an etch rate other than1:1. At step 301, as shown in FIG. 4A, a resist layer 407 is disposedover the device layer 408, the device layer 408 corresponding to theplurality of first structures 114, 214 and the plurality of secondstructures 115, 215 to be formed. In one embodiment, as shown in FIG.4B, the resist layer 407 is disposed over the substrate 101.

At step 302, the resist layer 407 is patterned to expose unmaskedportions of the device layer 408 as depicted in FIGS. 4C and 4D.Patterning the resist layer 407 includes forming a first resist layerpattern 422 having a plurality of first openings 420 formed therein overthe first portion 424 of the device layer 408, and forming a secondresist layer pattern 423 having a plurality of second openings 421formed therein over the second portion 425 of the device layer 408. Theresist layer 407 may be patterned by processes including, but notlimited to, nanoimprint lithography, photoimprint lithography, or anysuitable process to expose unmasked portions of the device layer 408. Inthe embodiment depicted in FIG. 4D, a residual layer 413 remains afterthe resist layer 407 is patterned. In one embodiment, the residual layer413 is removed through a dry etch process.

FIG. 4D illustrates an embodiment, in which an etch stop layer 406 isdisposed on the substrate 101. The etch stop layer 406 preventsover-etching into the substrate 101. The etch stop layer 406 may bedisposed by one or PVD, CVD, plasma-enhanced (PECVD), FCVD, ALD, andspin-on processes. The etch stop layer 406 is formed from any suitablematerial, provided that the etch stop layer 406 is resistant to theetching processes described herein. In one embodiment, the etch stoplayer 406 includes a nitrogen-containing material. In one embodiment,the etch stop layer 406 is a non-transparent etch stop layer that isremoved after the waveguide combiner is formed. In another embodiment,the etch stop layer 406 is a transparent etch stop layer. The etch stoplayer 406 has a depth of about 5 nm to about 50 nm. Although an etchstop layer 406 is depicted herein, one or more embodiments without anetch stop layer 406 is contemplated.

At step 303 and as shown in FIGS. 4C and 4D, the exposed portions of thedevice layer 408 defined by the plurality of first openings 420 and theplurality of second openings 421 are etched to form the plurality offirst structures 114, 214 and the plurality of second structures 115,215. The plurality of first openings 420 in the first resist layerpattern 422 are configured to form at least a portion of the pluralityof first structures 114, 214 within the optical device 100, 200. Theplurality of second openings 421 in the second resist layer pattern 423are configured to form at least a portion of the plurality of secondstructures 115, 215 within the optical device 100, 200. The etch processmay include, but is not limited to, at least one of ion implantation,ion beam etching (IBE), reactive ion etching (RIE), directional RIE,plasma etching, and thermal atomic layer etching. In some embodiments,the etch process utilizes oxidizing etch chemistries. In otherembodiments, the etch process utilizes reducing etch chemistries. In oneembodiment, the etch process utilizes one or more oxygen, nitrogen gas(N₂), SiO₂, chlorine, and ammonia (NH₃) containing gases. In anotherembodiment, a fluorine containing gas, such as fluoromethane (CH₃F),sulfur hexafluoride (SF₆), tetrafluoromethane (CF₄), fluoroform (CHF₃),and nitrogen trifluoride (NF₃), is used as an etchant. The fluorinecontaining gas is optionally delivered to a processing environment witha methane containing gas, such as methane (CH₄) anddichlorodifluoromethane (CCl₂F₂).

While FIG. 4E depicts first structures 114, 214 and second structures115, 215 formed in the device layer 408, steps 301-303 are applicable topatterning the substrate 101. In one embodiment, as shown in FIGS. 3 and4D, the device layer 408 is etched by the etch process to removeportions of the device layer 408 and form the first structures 114, 214and the second structures 115, 215 in step 303. In another embodiment,the substrate 101 is etched by the etch process to remove portions ofthe substrate 101 and form the first structures 114, 214 and the secondstructures 115, 215 in step 303.

FIG. 5 is a flow diagram of a method 500 for forming a portion of anoptical device 100, 200 according to embodiments described herein. FIGS.6A-6D are schematic, cross-sectional views of the optical device 100,200 formed according to the method 500. The portion of the opticaldevice 100, 200 may correspond to one grating, such as the first grating102 or second grating 105, or the portion may correspond to the entiretyof the optical device 100 or optical device 200.

At step 501, the hardmask 609 is disposed on the device layer 408 asshown in FIG. 6A. The hardmask 609 may be disposed over the device layer408 by one or more liquid material pour casting, spin-on coating, liquidspray coating, dry powder coating, screen printing, doctor blading, PVD,CVD, PECVD, FCVD, ALD, evaporation, and sputtering processes. In oneembodiment, the hardmask 609 is non-transparent and is removed after theoptical device 100 or optical device 200 is formed. In anotherembodiment, the hardmask 609 is transparent. In some embodiments, thehardmask 609 includes any suitable imprint-resist material, for examplechromium (Cr), silver (Ag), Si₃N₄, SiO₂, TiN, aluminum, and carboncontaining materials.

At step 502, the resist layer 407 is disposed on the hardmask 609, andthe device layer 408 corresponds to a plurality of first structures 114,214 and a plurality of second structures 115, 215 to be formed. Thedevice layer 408 has first height 411 and second height 412. In oneembodiment, the first thickness 409 and the second thickness 410 of theresist layer 407 are different such that the top surface 610 of theresist layer 407 is parallel to the top surface 118 of the substrate101. The top surface 610 of the resist layer 407 parallel to the topsurface 118 of the substrate 101 provides a planarized surface toimprove the uniformity of the patterning and/or etch process of steps503 and 504.

At step 503 and as shown in FIG. 6B, the resist layer 407 is patternedto expose portions of the hardmask 609. Patterning the resist layer 407includes forming the first resist layer pattern 422 having the pluralityof first openings 420 formed therein over the first portion 424 of thedevice layer 408, and forming the second resist layer pattern 423 havingthe plurality of second openings 421 formed therein over the secondportion 425 of the device layer 408. At step 504 and as shown in FIG.6C, the exposed portions of the hardmask 609 are etched to exposeunmasked first device layer segments 612 of the first portion 424 of thedevice layer 408 and to expose unmasked second device layer segments 613of the second portion 425 of the device layer 408. As shown in FIG. 6D,the first device layer segments 612 and the second device layer segments613 of the device layer 408 are etched to form the plurality of firststructures 114, 214 and the plurality of second structures 115, 215. Thefirst device layer segments 612 are configured to form at least aportion of the plurality of first structures 114, 214 within the opticaldevice 100, 200. The second device layer segments 613 are configured toform at least a portion of the plurality of second structures 115, 215within the optical device 100, 200.

In one embodiment, the hardmask 609 is removed after the device layer408 is etched. In another embodiment, the hardmask 609 remains on thedevice layer 408 after the device layer 408 is etched. While FIG. 6Ddepicts first structures 114, 214 and second structures 115, 215 formedin the device layer 408, steps 501-504 are applicable to patterning thesubstrate 101. In one embodiment, as shown in FIGS. 5 and 6D, the devicelayer 408 is etched by the etch process to remove portions of the devicelayer 408 and form the first structures 114, 214 and the secondstructures 115, 215 in step 504. In another embodiment, the substrate101 is etched by the etch process to remove portions of the substrate101 and form the first structures 114, 214 and the second structures115, 215 in step 504.

FIG. 7 is a flow diagram of a method 700 for forming a portion of anoptical device 100, 200 according to embodiments described herein. FIGS.8A-8D are schematic, cross-sectional views of the optical device 100,200 formed according to the method 700. The portion of the opticaldevice 100, 200 may correspond to one grating, such as the first grating102 or second grating 105, or the portion may correspond to the entiretyof the optical device 100 or optical device 200.

At step 701, the planarization layer 810 is disposed over the devicelayer 408 as shown in FIG. 8A, the device layer 408 corresponding to aplurality of first structures 114, 214 and a plurality of secondstructures 115, 215 to be formed. In one embodiment, the planarizationlayer 810 includes a-Si containing materials. The planarization layer810 may be deposited through any suitable process, including, but notlimited to, a liquid material pour casting process, a spin-on coatingprocess, a liquid spray coating process, a dry powder coating process, ascreen printing process, a doctor blading process, a PVD process, a CVDprocess, a PECVD process, a FCVD process, or an ALD process. Theplanarization layer 810 forms a top surface 812 parallel to thesubstrate 101 so that the planarization layer 810 prevents over-etchingof the device layer 408 in the etch process. At step 702, a resist layer407 is disposed over the planarization layer 810.

At step 703 and as shown in FIG. 8B, the resist layer 407 is patternedto expose portions of the planarization layer 810. Patterning the resistlayer 407 includes forming the first resist layer pattern 422 having theplurality of first openings 420 formed therein over the first portion424 of the device layer 408, and forming the second resist layer pattern423 having the plurality of second openings 421 formed therein over thesecond portion 425 of the device layer 408. At step 704 and as shown inFIG. 8C, the exposed portions of the planarization layer 810 defined bythe plurality of first openings 420 and the plurality of second openings421 are etched to expose unmasked first device layer segments 612 of thefirst portion 424 of the device layer 408 and second device layersegments 613 of the second portion 425 of the device layer 408.

In step 705 and as shown in FIG. 8D, the first device layer segments 612and the second device layer segments 613 of the device layer 408 areetched to form the plurality of first structures 114, 214 and theplurality of second structures 115, 215. The first device layer segments612 are configured to form at least a portion of the plurality of firststructures 114, 214 within the optical device 100, 200. The seconddevice layer segments 613 are configured to form at least a portion ofthe plurality of second structures 115, 215 within the optical device100, 200.

The etching includes, but is not limited to, one or more of ionimplantation, ion etching, reactive ion etching (RIE), directional RIE,and plasma etching. In one embodiment, planarization layer 810 has agreater etch selectivity than the device layer 408. While FIG. 8Ddepicts first structures 114, 214 and second structures 115, 215 formedin the device layer 408, steps 701-705 are applicable to patterning thesubstrate 101. In one embodiment, the device layer 408 is etched by theetch process to remove portions of the device layer 408 and form thefirst structures 114, 214 and the second structures 115, 215 in step705. In another embodiment, the substrate 101 is etched by the etchprocess to remove portions of the substrate 101 and form the firststructures 114, 214 and the second structures 115, 215 in step 705.

The embodiments described herein provide methods for multi-depth opticaldevices while minimizing defects associated with over-etching andnonuniformity.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method of forming an optical device,comprising: disposing a hardmask over a device layer disposed directlyover a planar top surface of a substrate, the device layer having: afirst portion having a first height from the top surface of thesubstrate; and a second portion having a second height from the topsurface of the substrate; disposing a resist layer over the hardmask,the resist layer having a top surface parallel to the top surface of thesubstrate; patterning the resist layer to: form a plurality of firstopenings therein over the first portion of the device layer to exposeportions of the hardmask; and form a plurality of second openings overthe second portion of the device layer to expose additional portions ofthe hardmask; etching the exposed portions of the hardmask to: expose aplurality of first device layer segments of the first portion of thedevice layer; and expose a plurality of second device layer segmentswithin the second portion of the device layer; and etching the firstdevice layer segments and the second device layer segments to expose atleast a portion of the planar top surface of the substrate; and formingat least a portion of a plurality of first structures within the opticaldevice, the first structures having a first depth relative to the topsurface of the substrate; and forming at least a portion of a pluralityof second structures within the optical device, the second structureshaving a second depth relative to the top surface of the substratedifferent than the first depth.
 2. The method of claim 1, wherein thefirst depth is less than the second depth.
 3. The method of claim 1,wherein the plurality of first structures and the plurality of secondstructures are perpendicular to the top surface of the substrate.
 4. Themethod of claim 1, wherein the plurality of first structures and theplurality of second structures are at an angle, other thanperpendicular, relative to the top surface of the substrate.
 5. Themethod of claim 1, wherein the hardmask is non-transparent.
 6. Themethod of claim 5, further comprising: removing the hardmask.
 7. Amethod of forming an optical device, comprising: disposing a hardmaskover a device layer disposed directly over a planar top surface of asubstrate, the device layer having: a first portion having a firstheight from the planar top surface of the substrate; and a secondportion having a second height from the planar top surface of thesubstrate; different from the first height disposing a resist layer overthe hardmask; patterning the resist layer to: form a plurality of firstopenings over the first portion of the device layer to expose portionsof the hardmask; and form a plurality of second openings over the secondportion of the device layer to expose additional portions of thehardmask; etching the exposed portions of the hardmask to: expose aplurality of first device layer segments within the first portion of thedevice layer; and expose a plurality of second device layer segmentswithin the second portion of the device layer; and etching the firstdevice layer segments and the second device layer segments to expose atleast a portion of the planar top surface of the substrate, whereinetching the first device layer segments comprises forming a plurality offirst structures within the optical device, the first structures havinga plurality of first openings there between, each of the first openingshaving a first depth; and etching the second device layer segmentscomprises forming a plurality of second structures within the opticaldevice, the second structures having a plurality of second openingsthere between, each of the second openings having a second depth whereinthe first depth is different than the second depth.
 8. The method ofclaim 7, wherein the first depth is less than the second depth.
 9. Themethod of claim 7, wherein a distance between the top surface and bottomsurface of the first structures is different from a distance between thetop surface and bottom surface of the second structures.
 10. The methodof claim 7, wherein the plurality of first structures and the pluralityof second structures are perpendicular to the planar top surface of thesubstrate.
 11. The method of claim 7, wherein the plurality of firststructures and the plurality of second structures are at an angle, otherthan perpendicular, relative to the top surface of the substrate. 12.The method of claim 7, wherein the hardmask remains on the device layerduring etching of the first device layer segments and the second devicelayer segments.
 13. A method of forming an optical device, comprising:disposing a hardmask over a device layer disposed directly over a planartop surface of a substrate, the device layer having: a first portionhaving a first height from the planar top surface of the substrate; anda second portion having a second height from the planar top surface ofthe substrate; disposing a resist layer over the hardmask, the resistlayer having a top surface parallel to the planar top surface of thesubstrate; patterning the resist layer to: form a plurality of firstopenings over the first portion of the device layer to expose portionsof the hardmask; and form a plurality of second openings over the secondportion of the device layer to expose additional portions of thehardmask; etching the exposed portions of the hardmask to: expose aplurality of first device layer segments within the first portion of thedevice layer; and expose a plurality of second device layer segmentswithin the second portion of the device layer; and etching the firstdevice layer segments and the second device layer segments to expose atleast a portion of the planar top surface of the substrate; and formingat least a portion of a plurality of first structures to expose a planarsurface within the optical device, the first structures having a firstdepth relative to the top surface of the substrate, wherein the hardmaskremains on the device layer; and forming at least a portion of aplurality of second structures to expose a planar surface within theoptical device, the second structures having a second depth relative tothe top surface of the substrate different than the first depth, whereinthe hardmask remains on the device layer.
 14. The method of claim 13,wherein the resist layer remains on the hardmask during etching ofexposed portions of the hardmask.
 15. The method of claim 13, whereinthe plurality of first structures and the plurality of second structuresare at an angle relative to the planar top surface of the substrate. 16.The method of claim 13, wherein the hardmask is non-transparent.